A man sits on a wall and enjoys the view.Dominic Ebenbichler / Reuters

In 2005, James Fallon's life started to resemble the plot of a well-honed joke or big-screen thriller: A neuroscientist is working in his laboratory one day when he thinks he has stumbled upon a big mistake. He is researching Alzheimer's and using his healthy family members' brain scans as a control, while simultaneously reviewing the fMRIs of murderous psychopaths for a side project. It appears, though, that one of the killers' scans has been shuffled into the wrong batch.

The scans are anonymously labeled, so the researcher has a technician break the code to identify the individual in his family, and place his or her scan in its proper place. When he sees the results, however, Fallon immediately orders the technician to double check the code. But no mistake has been made: The brain scan that mirrors those of the psychopaths is his own.

After discovering that he had the brain of a psychopath, Fallon delved into his family tree and spoke with experts, colleagues, relatives, and friends to see if his behavior matched up with the imaging in front of him. He not only learned that few people were surprised at the outcome, but that the boundary separating him from dangerous criminals was less determinate than he presumed. Fallon wrote about his research and findings in the book The Psychopath Inside: A Neuroscientist's Personal Journey Into the Dark Side of the Brain, and we spoke about the idea of nature versus nurture, and what—if anything—can be done for people whose biology might betray their behavior.

One of the first things you talk about in your book is the often unrealistic or ridiculous ways that psychopaths are portrayed in film and television. Why did you decide to share your story and risk being lumped in with all of that?

I'm a basic neuroscientist—stem cells, growth factors, imaging genetics—that sort of thing. When I found out about my scan, I kind of let it go after I saw that the rest of my family's were quite normal. I was worried about Alzheimer’s, especially along my wife’s side, and we were concerned about our kids and grandkids. Then my lab was busy doing gene discovery for schizophrenia and Alzheimer's and launching a biotech start-up from our research on adult stem cells. We won an award and I was so involved with other things that I didn't actually look at my results for a couple of years.

This personal experience really had me look into a field that I was only tangentially related to, and burnished into my mind the importance of genes and the environment on a molecular level. For specific genes, those interactions can really explain behavior. And what is hidden under my personal story is a discussion about the effect of bullying, abuse, and street violence on kids.

You used to believe that people were roughly 80 percent the result of genetics, and 20 percent the result of their environment. How did this discovery cause a shift in your thinking?

I went into this with the bias of a scientist who believed, for many years, that genetics were very, very dominant in who people are—that your genes would tell you who you were going to be. It's not that I no longer think that biology, which includes genetics, is a major determinant; I just never knew how profoundly an early environment could affect somebody.

While I was writing this book, my mother started to tell me more things about myself. She said she had never told me or my father how weird I was at certain points in my youth, even though I was a happy-go-lucky kind of kid. And as I was growing up, people all throughout my life said I could be some kind of gang leader or Mafioso don because of certain behavior. Some parents forbade their children from hanging out with me. They'd wonder how I turned out so well—a family guy, successful, professional, never been to jail and all that.

I asked everybody that I knew, including psychiatrists and geneticists that have known me for a long time, and knew my bad behavior, what they thought. They went through very specific things that I had done over the years and said, "That’s psychopathic." I asked them why they didn’t tell me and they said, "We did tell you. We've all been telling you." I argued that they had called me "crazy," and they all said, "No. We said you're psychopathic."

I found out that I happened to have a series of genetic alleles, "warrior genes," that had to do with serotonin and were thought to be at risk for aggression, violence, and low emotional and interpersonal empathy—if you're raised in an abusive environment. But if you're raised in a very positive environment, that can have the effect of offsetting the negative effects of some of the other genes.

Courtesy James Fallon

I had some geneticists and psychiatrists who didn't know me examine me independently, and look at the whole series of disorders I've had throughout my life. None of them have been severe; I’ve had the mild form of things like anxiety disorder and OCD, but it lined up with my genetics.

The scientists said, "For one, you might never have been born." My mother had miscarried several times and there probably were some genetic errors. They also said that if I hadn’t been treated so well, I probably wouldn’t have made it out of being a teenager. I would have committed suicide or have gotten killed, because I would have been a violent guy.

How did you react to hearing all of this?

I said, "Well, I don't care." And they said, "That proves that you have a fair dose of psychopathy." Scientists don't like to be wrong, and I’m narcissistic so I hate to be wrong, but when the answer is there before you, you have to suck it up, admit it, and move on. I couldn't.

I started reacting with narcissism, saying, "Okay, I bet I can beat this. Watch me and I'll be better." Then I realized my own narcissism was driving that response. If you knew me, you'd probably say, "Oh, he's a fun guy"–or maybe, "He's a big-mouth and a blowhard narcissist"—but I also think you'd say, "All in all, he's interesting, and smart, and okay." But here's the thing—the closer to me you are, the worse it gets. Even though I have a number of very good friends, they have all ultimately told me over the past two years when I asked them—and they were consistent even though they hadn’t talked to each other—that I do things that are quite irresponsible. It’s not like I say, Go get into trouble. I say, Jump in the water with me.

What's an example of that, and how do you come back from hurting someone in that way?

For me, because I need these buzzes, I get into dangerous situations.Years ago, when I worked at the University of Nairobi Hospital, a few doctors had told me about AIDS in the region as well as the Marburg virus. They said a guy had come in who was bleeding out of his nose and ears, and that he had been up in the Elgon, in the Kitum Caves. I thought, "Oh, that’s where the elephants go," and I knew I had to visit. I would have gone alone, but my brother was there. I told him it was an epic trek to where the old matriarch elephants went to retrieve minerals in the caves, but I didn't mention anything else.

When we got there, there was a lot of rebel activity on the mountain, so there was nobody in the park except for one guard. So we just went in. There were all these rare animals and it was tremendous, but also, this guy had died from Marburg after being here, and nobody knew exactly how he’d gotten it. I knew his path and followed it to see where he camped.

That night, we wrapped ourselves around a fire because there were lions and all these other animals. We were jumping around and waving sticks on fire at the animals in the absolute dark. My brother was going crazy and I joked, "I have to put my head inside of yours because I have a family and you don’t, so if a lion comes and bites one of our necks, it’s gotta be you."

Again, I was joking around, but it was a real danger. The next day, we walked into the Kitum Caves and you could see where rocks had been knocked over by the elephants. There was also the smell of all of this animal dung—and that’s where the guy got the Marburg; scientists didn't know whether it was the dung or the bats.

A bit later, my brother read an article in The New Yorker about Marburg, which inspired the movie Outbreak. He asked me if I knew about it. I said, "Yeah. Wasn’t it exciting? Nobody gets to do this trip." And he called me names and said, "Not exciting enough. We could've gotten Marburg; we could have gotten killed every two seconds." All of my brothers have a lot of machismo and brio; you’ve got to be a tough guy in our family. But deep inside, I don't think that my brother fundamentally trusts me after that. And why should he, right? To me, it was nothing.

After all of this research, I started to think of this experience as an opportunity to do something good out of being kind of a jerk my entire life. Instead of trying to fundamentally change—because it’s very difficult to change anything—I wanted to use what could be considered faults, like narcissism, to an advantage; to do something good.

What has that involved?

I started with simple things of how I interact with my wife, my sister, and my mother. Even though they’ve always been close to me, I don't treat them all that well. I treat strangers pretty well—really well, and people tend to like me when they meet me—but I treat my family the same way, like they're just somebody at a bar. I treat them well, but I don't treat them in a special way. That’s the big problem.

I asked them this—it's not something a person will tell you spontaneously—but they said, "I give you everything. I give you all this love and you really don’t give it back." They all said it, and that sure bothered me. So I wanted to see if I could change. I don't believe it, but I'm going to try.

In order to do that, every time I started to do something, I had to think about it, look at it, and go: No. Don’t do the selfish thing or the self-serving thing. Step-by-step, that's what I’ve been doing for about a year and a half and they all like it. Their basic response is: We know you don’t really mean it, but we still like it.

I told them, "You’ve got to be kidding me. You accept this? It’s phony!" And they said, "No, it’s okay. If you treat people better it means you care enough to try." It blew me away then and still blows me away now.

But treating everyone the same isn't necessarily a bad thing, is it? Is it just that the people close to you want more from you?

Yes. They absolutely expect and demand more. It's a kind of cruelty, a kind of abuse, because you're not giving them that love. My wife to this day says it's hard to be with me at parties because I've got all these people around me, and I'll leave her or other people in the cold. She is not a selfish person, but I can see how it can really work on somebody.

I gave a talk two years ago in India at the Mumbai LitFest on personality disorders and psychopathy, and we also had a historian from Oxford talk about violence against women in terms of the brain and social development. After it was over, a woman came up to me and asked if we could talk. She was a psychiatrist but also a science writer and said, "You said that you live in a flat emotional world—that is, that you treat everybody the same. That’s Buddhist." I don't know anything about Buddhism but she continued on and said, "It's too bad that the people close to you are so disappointed in being close to you. Any learned Buddhist would think this was great." I don't know what to do with that.

Sometimes the truth is not just that it hurts, but that it's just so disappointing. You want to believe in romance and have romance in your life—even the most hardcore, cold intellectual wants the romantic notion. It kind of makes life worth living. But with these kinds of things, you really start thinking about what a machine it means we are—what it means that some of us don't need those feelings, while some of us need them so much. It destroys the romantic fabric of society in a way.

So what I do, in this situation, is think: How do I treat the people in my life as if I'm their son, or their brother, or their husband? It's about going the extra mile for them so that they know I know this is the right thing to do. I know when the situation comes up, but my gut instinct is to do something selfish. Instead, I slow down and try to think about it. It's like dumb behavioral modification; there’s no finesse to this, but I said, well, why does there have to be finesse? I’m trying to treat it as a straightaway thing, when the situation comes up, to realize there’s a chance that I might be wrong, or reacting in a poor way, or without any sort of love—like a human.

A few years ago there was an article in The New York Times called, "Can You Call a 9-Year-Old a Psychopath?" The subject was a boy named Michael whose family was concerned about him—he'd been diagnosed with several disorders and eventually deemed a possible psychopath by Dan Waschbusch, a researcher at Florida International University who studies "callous unemotional children." Dr. Waschbusch examines these children in hopes of finding possible treatment or rehabilitation. You mentioned earlier that you don't believe people can fundamentally change; what is your take on this research?

In the '70s, when I was still a post-doc student and a young professor, I started working with some psychiatrists and neurologists who would tell me that they could identify a probable psychopath when he or she was only 2 or 3 years old. I asked them why they didn't tell the parents and they said, "There's no way I’m going to tell anybody. First of all, you can't be sure; second of all, it could destroy the kid’s life; and third of all, the media and the whole family will be at your door with sticks and knives." So, when Dr. Waschbusch came out two years ago, it was like, "My god. He actually said it." This was something that all psychiatrists and neurologists in the field knew—especially if they were pediatric psychologists and had the full trajectory of a kid's life. It can be recognized very, very early—certainly before 9-years-old—but by that time the question of how to un-ring the bell is a tough one.

My bias is that even though I work in growth factors, plasticity, memory, and learning, I think the whole idea of plasticity in adults—or really after puberty—is so overblown. No one knows if the changes that have been shown are permanent and it doesn't count if it's only temporary. It's like the Mozart Effect—sure, there are studies saying there is plasticity in the brain using a sound stimulation or electrical stimulation, but talk to this person in a year or two. Has anything really changed? An entire cottage industry was made from playing Mozart to pregnant women's abdomens. That's how the idea of plasticity gets out of hand. I think people can change if they devote their whole life to the one thing and stop all the other parts of their life, but that's what people can't do. You can have behavioral plasticity and maybe change behavior with parallel brain circuitry, but the number of times this happens is really rare.

So I really still doubt plasticity. I'm trying to do it by devoting myself to this one thing—to being a nice guy to the people that are close to me—but it's a sort of game that I’m playing with myself because I don't really believe it can be done, and it's a challenge.

In some ways, though, the stakes are different for you because you're not violent—and isn't that the concern? Relative to your own life, your attempts to change may positively impact your relationships with your friends, family, and colleagues. But in the case of possibly violent people, they may harm others.

The jump from being a "prosocial" psychopath or somebody on the edge who doesn't act out violently, to someone who really is a real, criminal predator is not clear. For me, I think I was protected because I was brought up in an upper-middle-class, educated environment with very supportive men and women in my family. So there may be a mass convergence of genetics and environment over a long period of time. But what would happen if I lost my family or lost my job; what would I then become? That's the test.

For people who have the fundamental biology—the genetics, the brain patterns, and that early existence of trauma—first of all, if they're abused they're going to be pissed off and have a sense of revenge: I don't care what happens to the world because I'm getting even. But a real, primary psychopath doesn't need that. They're just predators who don’t need to be angry at all; they do these things because of some fundamental lack of connection with the human race, and with individuals, and so on.

Someone who has money, and sex, and rock and roll, and everything they want may still be psychopathic—but they may just manipulate people, or use people, and not kill them. They may hurt others, but not in a violent way. Most people care about violence—that's the thing. People may say, "Oh, this very bad investment counselor was a psychopath"—but the essential difference in criminality between that and murder is something we all hate and we all fear. It just isn't known if there is some ultimate trigger.

And though there isn't an absolute "fix," you talk about the importance of the "fourth trimester"—the months following a baby's birth when bonding is key. What are other really crucial moments where you can see how someone may be at risk, or where this convergence of genetics and environment might be crucial for intervention, or at least identifying what is happening?

There are some critical periods in human development. For the epigenome, the first moment is the moment of conception. That is when the genetics are very vulnerable to methylation and, therefore, the effects of a harsh environment: the mother under stress, the mother taking drugs, alcohol, and things like that. The second greatest susceptibility is the moment of birth and, of course, there are the third and fourth trimesters. After that, there is a slow sort of susceptibility curve that goes down.

The first two years of life are critical if you overlap them with the emergence of what are called complex adaptive behaviors. When children are born they have some natural kinds of genetic programming. For example, a kid will show certain kinds of fear—of certain people, then of strangers, then it’s acceptance of people—that’s complex-adaptive behavior at work in social interactions. But even laughing, and smiling, and making raspberry sounds are all complex-adaptive behaviors, and they will emerge automatically. You don't need to be taught these things.

One idea is that over the first three years there are 350 very early complex adaptive behaviors that go in sequence, but if somehow you’re interrupted with a stressor, it will affect that particular behavior that’s emerging or just about to emerge. It could be at a year and half, 3 months, or 12 months. After that, the effects of environment really start to drop; by the time you start hitting puberty, you kind of get locked in. And during puberty your frontal lobe system does a switch.

Courtesy James Fallon

Before puberty, a lot of your brain–your frontal lobe and its connections—has to do with the orbital cortex, amygdala, and that lower half of the brain that controls emotional regulation. It is also the origin of people's natural sense of morality, when they learn regulation and the rules of the game, which are ethics. Before then, generally, a normal kid is very much living in a world of id—eating, drinking, some sexuality—but they’re also extremely moralistic. So, those are two things that are fighting each other those first years.

Courtesy James Fallon

Then, there’s a switch that occurs late in adolescence. For some people it could be 17, 18, 19, or 20-years-old. What happens is that the upper part of the brain, the frontal lobe and its connections, start to mature. That's a critical time because that’s usually when you see schizophrenia, some forms of depression, and those major psychiatric disorders emerge. For personality disorders it’s not really known when they will emerge because it’s very understudied. People will say, you can’t do anything about it, it’s locked in and there seems to be almost no treatment. Whereas, for things like depression, bipolar, schizophrenia, anxiety disorders, you can do something about it. There are drugs, or things you can do with brain stimulation and talk therapy, so that's where Big Pharma and the whole industry goes.

You start to really see personality disorders emerge around puberty, but for some children who might be primary psychopaths—that is, they have all the genes and their brain sort of set in the third trimester—this can start emerging very early, around 2 or 3-years-old. That is why we have to have more trained eyes—because that is where this becomes important for society.

A primary psychopath won't necessarily be dangerous, but if we can see that in a kid, we can tell parents to look for certain kinds of behavior. And if those behaviors emerge, we can safely discuss, protecting the privacy of that family and of the kid, how to have the child interact with a nurse practitioner or a trained professional. At that point, we can say: Make sure this kid is never bullied in school; keep them away from street violence, on and on.

A lot of kids, most kids, get bullied and they may get pissed off, but that doesn’t create a personality disorder. But there are 20 percent of kids who are really susceptible and they may ultimately be triggered for a personality disorder in puberty. If we know these children can be helped by making sure that they aren't abused or abandoned—because you've got to get there really early—well, then, that would be important to do. I don't mean to preach.

Well, go into the idea of preaching a little. You make a kind of grandiose statement at the beginning of your book that research into psychopaths, even with all of the privacy concerns, could have great implications for things from parenting to World Peace. What does that mean?

It means, for example, that if you have to go to war, and sometimes you probably have to go to war—I'm not talking about a belligerent country starting war or fomenting discord, but if you have to go to war and to engage infantry—you do not send 18-year-olds into it, because their brains aren't set. They don’t know how to adjudicate what's happening emotionally and hormonally with the intellectualization of it. When you're 20, 25, it’s a different matter because things gel a little more. Our emotions don't get away from us as much in terms of what is happening. Other factors, sociological ones like what soldiers return to, are also important, but we're not going to get rid of war any time soon, so we might as well engage in a way that does the least amount of damage.

In terms of legal action, you've been used as a researcher for court cases—not to determine guilt or innocence, but for sentencing. Do you think there’s a moral boundary for that since we don’t have enough knowledge on this field yet to determine guilt or innocence?

We don't have enough research. You can't just take genetics—even though I'm a big proponent of it—or imaging, and tell if someone's a criminal or a psychopath. If you put together all that information, you could explain a lot of behavior and causality and early abuse—but we don't know enough.

So, when I get a case to look at, first of all, I don't accept money—and it's not because I'm a nice guy. It's because I think I'd be biased. I don't accept any payment and I don't want to know who the person is. We all try to create a story or narrative, and I'm just as weak as anybody. I'll tell the defense attorney, or public defender, or whoever it is to just send me scans, maybe with normal scans to try to throw me off, and then I'll look at them and discuss what the traits of the person might be based on the lack of activity in certain areas or not.

I can usually say, "Oh, this person might have a language problem," or "This person might have trouble with impulsivity." After all of that analysis is there, we can look at their traits and see what they've done.

We've talked a lot about how to support a child that might be psychopathic, but what if the parent is the one whose brain resembles that of a psychopath? For example, what was it like for you to form attachments with your own children?

During the time when our kids were the most vulnerable, they remember a magical time with me. In talking about this, our three oldest children have said they thought I was the warm one who was always around and always interacting with them, and they don't understand how I could say that I was cold to them. But my wife and I were 21 when we got married. Things started changing for me when I was about 19 or 20-years-old, and it was really in my late 20s when the kids were older and took care of themselves more, that I took on a lot of these psychopathic qualities—though early on I clearly had some. My actual behavior didn't go south until later on, and I think my wife's stability kept things together.

Some people have this psychopathy or are almost psychopaths, and they get into trouble and go right to jail and end up in the prison system as 18-year-olds. It's awful because they get unlucky and they don't have enough impulse control to pull it back at the last instant. So, what is that edge where somebody's got these traits, and they are impulsive? What puts one guy on a pathway to becoming an attorney or successful in general, and the other one has life in prison? We just have to find out what that edge is. I think we will have parameters to work with, but it's not the same for everybody.

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